Sludge digestion tank



July 25, 1933. H. E. ELROD 1,919,639

7 V SLUDGE DIGESTION TANK Filed April 25, 1931 4 SheetsSheefc 1 Hwy137ml! Eh'lmunf July 25, 1933.

H. E. ELROD SLUDGE DIGESTION TANK Filed April 23, 1931 4 Sheets-Sheet 2176mg if Elma! July 25, 1933.

H. E. ELROD SLUDGE DIGESTION TANK Filed April 25, 1931 4 Sheets-Sheet 3July 25, 1933. H. E. ELROD 1,919,689

SLUDGE DIGESTION TANK Filed April 23, 1931 4 Sheets-Sheet. 4

' gwuenkvc of Fig. 1,

Patented July 25, 1933 i I UNITED STATES'PATENT OFFICE HENRY E. Emon, ornousron, TEXAS snunen mans-non ram:

Application filed .April 23, 1931 Serial R0. 532,375.

This invention relates to an improved ditank is also provided with oneor more congestion tank for treating sludge. ventional sealed entranceman-holes 5, as

It is an object of my invention to provide well as one or more sludgetesting and chemia digestion tank which allows the automatic cal dosingpipes 6. The floor 7 of my tank removal of the settled scum andsupernatant may be either flat or slightly sloping from liquor from thesludge settling chamber upthe inlet to the outlet end of the tan on theadmittance of additional sludge. As part of my tank structure, I rovideIt is a further object of my invention to 'an agitating system which Ihave dlsclosed provide a novel agitating means in conjuncin the form oftwo embodiments. In Fig. 1 tion with a sewage settling chamber to aidthis system consists of sprockets 10 mounted the bacterial digestionprocess that takes on shafts 11 which are in turn mounted place therein.transversely of the tank upon suitable brack- It is a further object ofmy invention to et members 12, clearly illustrated in Fig. 2. provide asettling tank in which the constitu- One of these shafts 11 is disposedat each 5 ent elements derived from sludge may be end of the tankadjacent the floor level there- 5 disposed of conveniently. of, with athird one shown at the center of Further objects and advantages of, mythe tank above the sludge level. Chains are structure will appear fromthe following deadapted to run over these sprockets and suittaileddescription of the embodiments of my able flights 9, preferably steelchannel sec- 0 invention in conjunction with the accomtions, areconnected across these chains and panying drawings wherein: are adaptedto extend throughout the width Fig. 1 is a sectional view across thelongiof the tank. Motion, in the direction of the tudinal axis of myimproved tank, arrows, is imparted to chains 8 by means of Fig. 2 is asectional viewalong line 2-2 a conventional prime mover. 13, such as anelectric motor, acting through driving con- Fig. 3 is a modified showingof the cover nections 14 and chain 15, thereby actuating structure inconjunction with a flat roof shaft 11 at the left end of the tank. Box16 forming the top of my tank, is provided to accommodate the chain orFig. i is a sectional view along line 4-4 eqmvalent drive 14, andextends below the $9 of Fig. 3, v roof 25 of the tank to' form a sealagainst Fig. 5 illustrates an alternate form of agithe escapement ofliquorand gases from tating and removing means for my layer of withintank 1. sludge material, a My tank is furthermore provided with one Fig.6 shows a detailed view of the reor more boxes 17 disposed at the topthereversing mechanism structure illustrated in of. Each such box or gasdome is provided Fig. 5. with the conventional sealed cover or hood Fig.7 is a sectional view along line 77 18, and gas discharge pipe 19 placedthereof Fig. 5, in, or at any other convenient point in the v Fig. 8 isa detailed side view of my gas dome above the liquor level. In one buggystructure mounting. form of my invention I provide a trou h Fig. 9 is aside view of Fig. 6 in conjunc- 20 extending transversely of the tankund er tion with the buggy housing. the gas dome and near the to of thetank.

In the drawings is illustrated the rectan- This trough may be made 0 anysuitable gular tank 1, adapted to hold sludge for material, althoughconcrete is preferable, digestion by bacterial action. The sludge and.may be provided with weir plates of may be admitted into the tankthrough one steel or other material. These troughs ma or more inletports 2. -One ormore convenbe disposed singly or ingroups. Eac tionaloutlets 3 are provided for leading trough 20 is provided with a. pipe 21which away the settled sludge. These may cooperconnects with aconventional seal trap 22 ate with hoppers 4 near the outlet end. Thisprovided with a discharge pipe 23. For this trough may also besubstituted a plurality of upright pipes 26, shown in Fig. 3, with orwithout flared inlets 27. These pipes may in turn be connected by meansof an outlet pipe 21, as is the case with the troughs, with a suitableseal trap and discharge pipe, as illustrated in Fig. 4. The

showings of Figs. 3 and 4 show my tank provided with a flat form ofroof, which in nowise alters the mode of operation of my system which isas follows. The sludge is admitted to the tank from previously disposedcollecting tanks through the'inlet port either by means of a gravity ora forced feed. Upon being filled, the resulting process of bacterialdigestion takes place, at which time the sludge divides itself intothree layers. At the top, is found a layer of scum. Below it is a layerof supernatant liquors, and the lowermost layer is that of sludge. Thegases that are evolved during this digestion process rise to the top ofthe gas domes 17 and are suitably passed off either to the atmosphere orto proper reservoirs by means of pipes 19. After a certain period whenthe process is completed, additional sludge is admitted into the chamberwhich results in the forcible raising of the layers of scum andsupernatant liquors over the sides of the trough 20 or equivalentelements, thereby automatically removing said liquors for properdistribution and providing room for the new batch to be operated upon.Sludge eduction pipes 24 may be provided in addition to outlet 3 forwithdrawing sludge at various elevations.

My process of digesting is greatly aided by intermittently agitating thesolid matter in the tank. A conventional form of chain mixer provedimpractical in this 'type of tank, for the reason that such generallyconsisted of horizontal tracks against the wall of the tank upon whichthe chain could travel directly from one sprocket to the other at theopposite ends of the tank adj acent the floor level. With this type ofmovement it was necessary that a tightening device be provided in orderto keep the chain taut and prevent it from buckling. In view of thelocation of such a device, it was inaccessible, and furthermore its modeof operation was difficult to observe. With my arrangement disclosedherein, the chain is kept taut by its weight, suspended from the topsprockets 10, and no tighteners are necessary. The present arrangementalso offers the great advantage that the complete layer of sludge ismixed and agitated throughout its depth during the chain movement. Withthe conventional horizontal chain travel, only that portion of thesludge layer was agitated which extended between the upper and lowerflights of the chain.

My agitating system also erforms the function of cleaning, since the'ghts 9 drag the floor 7 of the tank, and when the sludge is beingwithdrawn, all settled inorganic and other matter will be scrapedtherefrom. This obviates the necessity for the manual cleaning of thetank which is a very arduous task.

In Figs. 5 to 9, I have illustrated an alternative mode of agitating andremoving my settled sludge layer. These figures do not illustrate theother features of the tank shown in detail in Figs. 1 to 4. Theagitating element consists of a buggy 31 constructed preferably of steelstructural members riveted or welded together. The body of thistravelling member or 'buggy is mounted on wheels 32 which are adapted totravel upon rails 33 laid on the floor of the tank or suspended from theside walls thereof upon suitable brackets. This travelling member mayassume the alternative form of a sled, adapted to slide directly on thefloor of the tank and between the walls thereof. A blade or scraper 34is hinged from the travelling member 31 and extends downwardly to suchan extent that it just clears the floor of the tank. Upon the travellingmember structure is fixed a stop 37 which is adapted to engage thispivoted member 34 in the direction of travel toward the outlet end, butwhich will not interfere with the blade 34 when the member travels inthe opposite direction. Thus in its movement toward the outlet end, themember-34 will push the sludge in front of it toward that end, whereasupon the reverse movement of the buggy, it will be free to slide overthe sludge.

A flexible member 38, preferably an ordinary round link chain, isfixedly attached to both ends of buggy 31 at its center, or optionallytwo such flexible members may be connected at the two sides of each end.Elements 38 are threaded through rag wheels or sheaves 39, the strandsof which are anchored into the walls, substantially as shown. Pipes 40are provided for the flexible member 38 to pass from the inside to theoutside of the tank, serving to act as seals to prevent the escape ofgases from the tank. Outside of the tank, element 38 passes over a ragwheel 41 suitably mounted and connected to any conventional motor orother prime mover 42 connected through an intermediate gear reducer 43,if such is necessary. Of course, element 38 may be actuated by amanually operated winch or equivalent means.

In the case of a motor actuation for element 38, it is necessary thatthe travelling member or buggy 31 be reversed at its limits of travel.For this purpose, a shaft 44 is provided, against one wall of the tankby means of anchors 45, which allow longitudinal motion of shaft 44therein. Stop pawls 46 are fixedly attached to shaft 44 near theextremities of the tank. The change link Patent No. 1,700,791, February5, 1929, de-

pendent upon operating conditions. By this means, I obtain an eificientagitating as well as ejecting mechanism for my layer of settled sludge.

Having described my invention,

I claim:

1. In a sludge digestion tank, an inlet for the reception of liquidsludge, an outlet adjacent the bottom of the tank for the eduction ofsettled sludge, a gas-tight cover for said tank, a gas collecting domedisposed in and above said cover, means for withdrawing the gasescollected in said gas dome, an outlet for supernatant liquor and scumsegregated from said liquid sludge disposed within said gas dome andwith the mouth thereof above the normal level of the supernatant liquor,and a liquid seal trap for sealing said outlet against the escapement ofgases from within the tank and from the ingress of air from the exteriorto the interior of the tank.

2. In a sludge digestion tank, an inlet for the reception of liquidsludge, an outlet adjacent the bottom of the tank for the eduction ofsettled sludge, agitating means for said sludge, a gas-tight cover forsaid tank, a gas collecting dome disposed in and above dome and withsaid cover, means for withdrawin the gases collected in said gas dome,an out et for supernatant liquor and scum se egated from said liquidsludge disposed within said gas the mouth thereof above the normal levelof the supernatant liquor, and a liquid seal trap for sealing saidoutlet against the escapement of gases from within the tank and from theingress of air from the exterior to the interior of the tank.

3. The combination with a sludge digestion tank as claimed in claim 2wherein the agitating means for the settled sludge comprises sprocketrollers at extreme ends of said tank adjacent the floor level thereof, asprocket roller above the sludge level intermediate the extreme ends ofsaid tank, a chain comprising transverse channel elements passing oversaid rollers, and means for actuating said chain.

4. The combination with a sludge digestion tank as claimed in claim 2wherein the agitating means for the settled sludge comprises atravelling member, means for actuating said travelling member in twodirections, a pivoted plate suspended from the top thereof, a stopelement on said member adapted to retain said plate .in a vertical.position in the course of movement thereof from the entrance to theexit end of said tank, said element being freely ivoted in its reversedirection, and means its reversing the direction of said member at itslimits of travel.

HENRY E. ELROD.

